1. Field of the Invention
This invention relates to new and improved bearing assemblies. More particularly, the invention relates to a new and improved bearing assembly comprising means for positively lubricating various moving elements of the assembly and for positively indexing load-bearing segments of the assembly. The bearing assembly of the present invention is particularly useful for supporting large loads such as those encountered by bearings which attach the cutting wheels to a rotary drill bit. Many other uses are also comtemplated.
2. Brief Description of Prior Art
A variety of different bearing assemblies are known in the art, including some specifically adapted for supporting large loads.
U.S. Pat. Nos. 3,549,214 and 3,476,446 are examples of floating segmented bearing assemblies comprising bearing segments retained in a torus between raceways of a rotating cutter wheel and a journal pin of a rotary drill bit. The bearing segments provide enlarged load-bearing surface area to withstand high loads.
High speed bearings usually employ rotational elements such as balls or rollers which rotate between the two relatively rotating race members and support the race members with respect to one another. The antifriction rotational elements divide the relative motion of the raceway members between two or more pairs of contact surfaces and reduce the speed of relative movement at each contact surface, thereby allowing bearing operation at high speeds. Rotational load-bearing elements have limited load carrying capacity. The contact of the rotational balls or rollers with the race members at essentially a point or line concentrates the bearing load on a very small surface area, and damage to the bearing structure will eventually result if the load is not limited.
In order to assure that the rotational elements move at a differential speed during relative rotation of the race members, it is known to slightly compress or preload the rotational elements between the two race members. U.S. Pat. Nos.4,410,618; 3,765,071; 3,930,693 and 4,002,380 disclose hollow compressible rotational elements in bearing assemblies, and U.S. Pat. No. 4,133,587 discloses elastic non-hollow rotational elements. Elastic rotational elements are also utilized in a Hyatt bearing described in Mechanical Designs of Machines by Siegel, Maleeve and Hartman, International Textbook Co., Scranton, Pennsylvania, 4th edition, p. 455. Of course, hollow or very soft rotational elements are structurally incapable of withstanding very large loads before destruction. On the other hand, solid inflexible rotational elements cannot resiliently deform a sufficient amount to maintain compression force between the race members when passing through areas of large variations in clearance in the bearing.
Bearing assemblies combining both compressible roller elements and sliding bearing elements are disclosed in U.S. Pat. Nos. 3,301,611; 4,133,587; 2,373,860 and 1,946,652. Although some of these combination bearing constructions achieve a limited measure of cooperation between the roller elements and the bearing segments, an increased degree of operative interaction between the elements and enhanced bearing performance under the application of high loads are desirable. In the field of rotary drill bits and rotary drilling there is a substantial and continuing need for improved bearings that increase the useful lifetime of drill bits.
In any bearing assembly adequate lubrication is important to obtain good performance and longevity of use. The lubricant should be continuously applied over all the moving and load bearing surfaces. A variety of different lubricating arrangements for bearings are disclosed in U.S. Pat. Nos. 3,244,459; 3,301,611; 3,890,018; 3,663,073; 3,251,634; 3,746,405; 3,845,994; 3,866,987; 3,719,241; 4,033,646 and 4,074,922, and by the Hyatt bearing. Many of these lubricating devices employ additional apparatus in conjunction with the bearing assembly, or are not suitable for convenient incorporation into a bearing assembly, or are not as effective as is now possible.
It is apparent that various features, arrangements and apparatus are known in the field of bearing assemblies. Comprehension of these prior art arrangements should lead to an enhanced appreciation of the significance of the present invention and its improvements and advancements in the art.